General help message cleanup

Many of the help messages were not really helpful; for example, many
commands that take no arguments would not print a correct synopsis
line, but "No additional help available." which is not exactly wrong,
but not helpful either.

Commit ``Make "usage" messages more helpful.'' changed this
partially. But it also became clear that lots of "Usage" and "Help"
messages (fields "usage" and "help" in struct cmd_tbl_s respective)
were actually redundant.

This patch cleans this up - for example:

Before:
	=> help dtt
	dtt - Digital Thermometer and Thermostat

	Usage:
	dtt         - Read temperature from digital thermometer and thermostat.

After:
	=> help dtt
	dtt - Read temperature from Digital Thermometer and Thermostat

	Usage:
	dtt

Signed-off-by: Wolfgang Denk <wd@denx.de>
diff --git a/board/amirix/ap1000/powerspan.c b/board/amirix/ap1000/powerspan.c
index f727061..28e2bbc 100644
--- a/board/amirix/ap1000/powerspan.c
+++ b/board/amirix/ap1000/powerspan.c
@@ -487,7 +487,7 @@
 	    "    - store contents of eeprom at address ADD\n"
 	    "eeprom p ADD\n"
 	    "    - put data stored at address ADD into the eeprom\n"
-	    "eeprom d\n" "    - return eeprom to default contents\n");
+	    "eeprom d\n" "    - return eeprom to default contents");
 
 unsigned int PowerSpanRead (unsigned int theOffset)
 {